Staging: hv: remove function pointer typedefs from vmbus.h

It's amazing the hoops that people go through to make code work
when they don't opensource the whole thing.  Passing these types
of function pointers around for no good reason is a mess, this needs
to be unwound as everything is now in the open.

Cc: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>